Surface acoustic wave device

Abstract

A surface acoustic wave device comprises a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on the surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are an Eulerian angle representation of (0°-45°, 30°-90°, 40°-90°) and directions equivalent thereto, the surface acoustic wave having higher propagation velocity than Rayleigh waves and leaky waves, and a characteristic of radiating part of energy of the surface acoustic wave into the piezoelectric surface while propagating.

What is claimed is: 
     
       1. A surface acoustic wave device comprising a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on a surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are an Eulerian angle representation of (0°-45°, 38°-55°, 80°-90°) and directions equivalent thereto,   a propagation velocity of the surface acoustic wave being higher than a propagation velocity of a fast shear bulk wave propagating in the same direction as the surface acoustic wave and not exceeding that of a longitudinal bulk wave.   
     
     
       2. A surface acoustic wave device according to claim 1, wherein the metal film are so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are an Eulerian angle representation of (0°-45°, 45°-50°, 80°-90°) and directions equivalent thereto. 
     
     
       3. A surface acoustic wave device according to claim 2, wherein the metal film are so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are an Eulerian angle representation of (0°-2°, 45°-50°, 88°-90°) and directions equivalent thereto. 
     
     
       4. A surface acoustic wave device according to claim 1, wherein the metal film are formed of a metal containing aluminium as the main component, and the metal film have a normalized film thickness of below about 8%. 
     
     
       5. A surface acoustic wave device according to claim 2, wherein the metal film are formed of a metal containing aluminium as the main component, and the metal film have a normalized film thickness of below about 8%. 
     
     
       6. A surface acoustic wave device according to claim 4, wherein the metal film are formed of a metal containing aluminium as the main component, and the metal film have a normalized film thickness of 0.5-3.5%. 
     
     
       7. A surface acoustic wave device according to claim 5, wherein the metal film are formed of a metal containing aluminium as the main component, and the metal film have a normalized film thickness of 0.5-3.5%. 
     
     
       8. A surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is a transversal filter having a electrode formed of the metal film. 
     
     
       9. A surface acoustic wave device according to claim 2, wherein the surface acoustic wave device is a transversal filter having a electrode formed of the metal film. 
     
     
       10. A surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is a delay line having a electrode formed of the metal film. 
     
     
       11. A surface acoustic wave device according to claim 2, wherein the surface acoustic wave device is a delay line having a electrode formed of the metal film. 
     
     
       12. A surface acoustic wave device comprising a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on a surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave area are an Eulerian angle representation of (0°-45°, 30°-75°, 40°-90°) and directions equivalent thereto,   a propagation velocity of the surface acoustic wave being higher than a propagation velocity of a fast shear bulk wave propagating in the same direction as the surface acoustic wave and not exceeding that of a longitudinal bulk wave.   
     
     
       13. A surface acoustic wave device comprising a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on a surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagating direction of the surface acoustic wave are an Eulerian angle representation of (0°-45°, 30°-75°, 40°-90°) and directions equivalent thereto,   a propagation velocity of the surface acoustic wave being higher than a propagating velocity of a fast shear bulk wave propagating in the same direction as the surface acoustic wave and not exceeding that of a longitudinal bulk wave.   
     
     
       14. A surface acoustic wave device comprising a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on a surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are an Eulerian angle representation of (0°-45°, 30°-90°, 40°-65°) and directions equivalent thereto,   a propagation velocity of the surface acoustic wave being higher than a propagation velocity of a fast shear bulk wave propagating in the same direction as the surface acoustic wave and not exceeding that of a longitudinal bulk wave.   
     
     
       15. A surface acoustic wave device according to claim 12, wherein the metal film are formed of a metal containing aluminum as the main component, and the metal film have a normalized film thickness of below about 8%. 
     
     
       16. A surface acoustic wave device according to claim 13, wherein the metal film are formed of a metal containing aluminum as the main component, and the metal film have a normalized film thickness of below 8%. 
     
     
       17. A surface acoustic wage device according to claim 14, wherein the metal film are formed of a metal containing aluminum as the main component, and the metal film have a normalized film thickness of below about 8%. 
     
     
       18. A surface acoustic wave device according to claim 15, wherein the metal film are formed of a metal containing aluminum as the main component, and the metal film have a normalized film thickness of 0.5-3.5%. 
     
     
       19. A surface acoustic wave device according to claim 16, wherein the metal film are formed of a metal containing aluminum as the main component, and the metal film have a normalized film thickness of 0.5-3.5%. 
     
     
       20. A surface acoustic wave device according to claim 17, wherein the metal film are formed of a metal containing aluminum as the main component, and the metal film have a normalized film thickness of 0.5-3.5%. 
     
     
       21. A surface acoustic wave device according to claim 12, wherein the surface acoustic wave device is a transversal filter having a electrode formed of the metal film. 
     
     
       22. A surface acoustic wave device according to claim 19, wherein the surface acoustic wave device is a transversal filter having a electrode formed of the metal film. 
     
     
       23. A surface acoustic wave device according to claim 14, wherein the surface acoustic wave device is a transversal filter having a electrode formed of the metal film. 
     
     
       24. A surface acoustic wave device according to claim 12, wherein the surface acoustic wave device is a delay line having a electrode formed of the metal film. 
     
     
       25. A surface acoustic wave device according to claim 13, wherein the surface acoustic wave device is a delay line having a electrode formed of the metal film. 
     
     
       26. A surface acoustic wave device according to claim 14, wherein the surface acoustic wave device is a delay line having a electrode formed of the metal film. 
     
     
       27. A surface acoustic wave device comprising a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on a surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are on Eulerian angle representation of (0°-45°, 30°-70°, 40°-90°) and directions equivalent thereto,   a propagation velocity of the surface acoustic wave being higher than a propagation velocity of a fast shear bulk wave propagating in the same direction as the surface acoustic wave and not exceeding that of a longitudinal bulk wave.   
     
     
       28. A surface acoustic wave device comprising a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on a surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are an Eulerian angle representation of (0°-45°, 38°-55°, 40°-90°) and directions equivalent thereto,   a propagation velocity of the surface acoustic wave being higher than a propagation velocity of a fast shear bulk wave propagating in the same direction as the surface acoustic wave and not exceeding that of a longitudinal bulk wave.